Breathing is controlled automatically (reflexly) but can also be affected by voluntary actions (is under voluntary control). Voluntary control may be particularly important in the dyspneic patient with chronic obstructive lung disease. This proposal examines the hypothesis that in patients with COLD breathing patterns (which were initially deliberately chosen to avoid dyspnea) can become habitual and occur without conscious awareness. In some patients voluntary choice of breathing patterns may lead to worsening of alveolar hypoventilation. Six sets of experiments to be performed in humans are proposed. In the first set of experiments differences in the perception of respiratory movement in patients and normals are examined and related to intensity of dyspnea. The second and third set evaluate the automatic regulation of breathing, asleep and awake. The fourth set of studies assesses the interactions of voluntary and automatic regulation of breathing in different situations in which the drive to breathing is altered. Voluntary control of breathing may be limited in the dyspneic patients with respiratory failure. Therefore, in the fifth set of experiments the effects of chronic lung disease on the ability to voluntarily target the movement of the respiratory muscles is assessed and compared to the capacity of patients and normals to perform skilled movement with the extremities. In the final set of experiments in humans the effects of interventions which alter respiratory muscle performance are assessed to determine whether performance affects dyspnea, or the ability to control the respiratory muscles either automatically or voluntarily. A series of studies in animals are also proposed to investigate the functional nervous pathways that might affect the tightness of the automatic regulation of breathing and the degree to which lesions in these pathways affect the interaction of the respiratory and circulatory systems which maintain constancy of O2 and CO2 levels in the body.